Genuine Possibilities in the Scientific Past and How to Spot Them.

The extent to which we take counterfactual history seriously depends on how well grounded we take the relevant possibilities to be. Beginning with a general consideration of the relationship between conceivability and possibility, this essay examine the grounds on which these alternative histories might be based. Drawing on examples from physics, such as the Bohmian version of quantum theory and the parastatistics approach to quarks, it suggests that such grounds are not as firm as might be thought and that further work is required in both the history and the philosophy of science before the putative alternatives can be taken as "genuine" possibilities. [ABSTRACT FROM AUTHOR]